ARYA Atherosclerosis3220101208EFFECT OF AMLODIPINE ON BLOOD AND RENAL TISSUE CONCENTRATIONS OF ENDOTHELIN IN MALE RABBITS RECEIVING AN ATHEROGENIC DIET108108ENMustafaMohammadiPh.D. Associate Professor, Department of Physiology, Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.. m.mohammadin@yahoo.comFaribaMirzaei20101204  Abstract INTRODUCTION: Recent studies indicate that endothelin-1 (ET-1) and abnormality in the transfer of calcium ions have a role in the atherosclerosis process. Amlodipine can influence the risk factors associated with atherosclerosis, but the possible protective mechanisms of ET-1 are not known. We evaluated the effects of amlodipine and/or high-cholesterol diet on blood and renal tissue concentration of endothelin, as well as the role of ET-1 in the pathophysiology of atherosclerosis in male New Zealand white rabbits. methods: Thirty-six male New Zealand white rabbits were divided into four groups: The normal control group, normal group receiving amlodipine, high-cholesterol diet group and high-cholesterol diet plus amlodipine group. After 8 weeks, all animals were anesthetized and blood or tissues samples were colleted. results: Amlodipine led to significant increase in plasma high-density lipoprotein cholesterol (HDL-C) and decrease in serum triglyceride (TG) in the control group. The plasma level of ET-1 in the atherosclerotic model group increased significantly compared with the control group (p<0.01). After 8 weeks of treatment with amlodipine, ET-1 levels decreased significantly in the control group (p<0.01) and high-cholesterol diet rabbits (p<0.01). Amlodipine administration significantly reduced the tissue levels of endothelin only in high-cholesterol diet rabbits (p<0.01). Eight weeks of high-cholesterol diet (2%) did not induce any atherosclerotic lesion in this artery, and amlodipine had no significant effect. CONCLUSIONS: The increase of lipids and ET-1 in the renal artery and plasma with a high-cholesterol diet is not linked to the early stages of atherosclerotic plaque formation. Amlodipine can reduce levels of ET-1 and lipids, but the mechanisms remain to be determined.     Keywords: Renal artery, atherosclerosis, amlodipine, endothelin-1, experimental study.